Problem: A volunteer group is planting trees at $6$ different parks. They planted $70$ trees at each park. How many trees did the group plant in all?
${70}$ trees is the same as ${7\text{ groups of ten}}$ trees. There are $6$ parks. Total number of trees: $\begin{aligned}&6\times{7\text{ groups of ten}}\\ =&{42\text{ groups of ten}}\\ =&{420}\end{aligned}$ The group planted ${420}$ trees.